1. Field of the Invention
The present invention relates to enhancement of fluid flow through a duct by the inclusion of a high surface energy material, and more specifically to enhancement of ink flow through tubing of thermal ink jet printing devices.
2. Description of Related Art
In thermal ink jet printing devices, it is necessary to be able to turn ink flow on and off between an ink supply reservoir and a printhead. In a typical ink supply system, when the ink flow shuts off, slugs of ink, separated by air pockets, form in the duct or supply tube communicating the ink between the reservoir and the printhead. These slugs of ink prevent ink flow from being re-established. This is due to the forces of wetting and surface tension acting on the inner walls of the duct and the slugs.
A possible solution to the problem would be to pressurize the ink reservoir. This however requires extra cost and complexity.
The force of adhesion, i.e., wetting of the tube walls, could also be reduced by coating the walls of the tube with a low surface energy material, such as RAIN-X, however such a solution will not be perfect and will not produce much benefit because the wetting forces are small compared with surface tension forces.
Another option would be to make the walls of the tube as smooth as possible in order to minimize the forces of wetting. This option is time consuming, costly, and still does not substantially reduce forces.
There is a need for a simple, low cost device which enhances the re-establishment of fluid flow in the duct.